Skin cleansing compositions routinely include abrasive particles for a variety of reasons such as cleansing the skin (e.g., removal of dirt, sebum, or oil) or improving the appearance of the skin (e.g., exfoliation). Abrasive particles are commonly made from petroleum-based synthetic polymers like polystyrene or cross-linked styrene (XST) and/or polyurethane (PU), polyolefins plastic or waxes, etc. Unfortunately, these petroleum-based synthetic polymers may pose long-term disposal problems and could have adverse effects on the environment. On the other hand, natural abrasives like abrasives derived from plants or shells e.g.: from nuts or otherwise abrasive based on mineral material, present poor aesthetic and/or potential allergenic issues or are too abrasive for usage onto facial skin.
Recently, biobased polymers like polyhydroxy alkonates (PHA) have attracted significant attention because they are made from renewable resources (e.g., plants), and can be recycled using biological processes (i.e., biorenewable or biodegradable) to reduce greenhouse gas emission and conserve limited resources. On account of the current market demands for more green alternatives, the consumer goods industry has started to use biobased polymers as abrasive particles in fabric and home care products for cleaning dishes, clothes, and hard surfaces (see for example US2013/317736 (P&G) and JP 04-331294 (Three Bond)).
The use of biobased polymers as abrasive particles (i.e., “biodegradable abrasive particles”) in skin cleansing compositions, particularly facial cleansers, has remained largely unexplored.
Existing biodegradable abrasive particles of the types disclosed in JP 04-331294 were designed for certain fields of application (e.g., hard surface cleaning, detergents for dish or clothes) which require scouring of stains, preferably hard to remove stains or soils, deposited on inanimate surfaces. Reapplication of the same biodegradable abrasive particles for use in skin cleansing composition would not be appropriate, as they tend to be overly abrasive and can damage the skin, especially when applied on facial skin surface, which is more sensitive.
Conversely, less aggressive biodegradable abrasive particles may yield poor and/or inadequate cleansing performance as evidenced by soil or make-up remaining on the skin after use. Furthermore, existing biodegradable abrasive particles often have an undesirable texture for skin cleansing compositions. For example, consumers selecting a facial cleanser may avoid compositions that feel gritty or overly coarse or succetible to create allergenic reaction for instance, but not limited to natural exfoliant containing protein. Formulators often must choose between overly abrasive particles that may cause damage on the skin surface, and gentler abrasive particles with a better sensorial feel but with reduced, perhaps inadqueate, cleansing efficacy. In addition, such currently known biodegradable abrasive particles are not selected for various stability, aesthetics, and/or compatibility with other materials commonly present in the personal care composition field and therefore would likely not be considered dermatologically acceptable.
Therefore, there is a need for a new skin cleansing composition, preferably a facial cleansing composition, comprising biodegradable abrasive particles, having skin cleansing and/or exfoliating benefits when applied on skin surfaces, preferably facial skin surfaces. There is also the need for a new skin cleansing composition, preferably a facial cleansing composition, having a sufficiently acceptable surface safety profile and is dermatologically acceptable. It is also highly desirable that the total skin cleansing composition is biodegradable, preferably in addition to the abrasive particles being biodegradable.